Movintgt, that's correct. Tire pressures need to vary with the weight they support. This is easily evident when you think of the front tires on a tractor with a FEL compared to the ones on a tractor with a 3PH mounted implement. What's correct for one is totally inappropriate for the other. It holds true for rear tires as well, of course.
I posted this before in this thread, post#16 to be exact...
"Tires are designed to operate at maximum efficiency when they are at their Rated Deflection. With the tractor on a hard surface, deflection is the distance from the axle center to the ground surface divided by the distance from the axle center to the top of the tire. In technical terms, deflection is the value of the loaded radius of the tire compared to the unloaded radius. Rated deflection is the amount of deflection when the tire is deformed to its optimum or design footprint. Rated deflection for radial tires is about 85%, for bias tires it is about 90%. The correct pressure to achieve rated deflection depends on the load the tire is carrying. A correctly inflated radial tire will have a significant sidewall bulge or "cheek'. It may look low or flat but it is not. If you inflate a radial tire by "eyeball" until the sidewall bulge looks like that of a bias ply tire, you lose most of the performance advantages of the radial tire."